A finite-element-simulation for pulse amplification in ytterbium-doped double-clad fiber amplifier is presented by means of (finite element modeling laboratory )FEMLAB package. The upper-level population distributions, the pump power, and the amplified spontaneous emission while under forward pumping with 915 nm are investigated. The transient output power, stored energy and gain of both Gaussian and square pulse are simulated. The obtained results are agreement well with the results reported in the experimental and other numerical studies.